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Overview
Comment:Fix an assert() in unlockBtreeIfUnused() so that it checks for the existance of an untripped cursor, not for the existance of any cursor at all.
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SHA1: a6f851d0fe01d8c8d44a2fe0b716ff7a5194c63b
User & Date: drh 2013-05-14 23:12:06
Context
2013-05-14
23:13
Merge together the fork in this branch. check-in: 164e3d4d user: drh tags: shared-cache-fixes
23:12
Fix an assert() in unlockBtreeIfUnused() so that it checks for the existance of an untripped cursor, not for the existance of any cursor at all. check-in: a6f851d0 user: drh tags: shared-cache-fixes
2013-05-13
18:23
Candidate fixes for problems revealed by notify2.test. Notify2.test is still failing at this point. check-in: ea0428f9 user: dan tags: shared-cache-fixes
Changes
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Changes to src/btree.c.

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page1_init_failed:
  releasePage(pPage1);
  pBt->pPage1 = 0;
  return rc;
}
























/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which 
** has the effect of releasing the read lock.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( pBt->pCursor==0 || pBt->inTransaction>TRANS_NONE );
  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
    assert( pBt->pPage1->aData );
    assert( sqlite3PagerRefcount(pBt->pPager)==1 );
    assert( pBt->pPage1->aData );
    releasePage(pBt->pPage1);
    pBt->pPage1 = 0;
  }
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeCommitPhaseTwo(p, 0);
  }
  sqlite3BtreeLeave(p);
  return rc;
}

#ifndef NDEBUG
/*
** Return the number of write-cursors open on this handle. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** For the purposes of this routine, a write-cursor is any cursor that
** is capable of writing to the databse.  That means the cursor was
** originally opened for writing and the cursor has not be disabled
** by having its state changed to CURSOR_FAULT.
*/
static int countWriteCursors(BtShared *pBt){
  BtCursor *pCur;
  int r = 0;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( pCur->wrFlag && pCur->eState!=CURSOR_FAULT ) r++; 
  }
  return r;
}
#endif

/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on BtShared that pBtree
** references.
**
** Every cursor is tripped, including cursors that belong
** to other database connections that happen to be sharing
................................................................................
      int nPage = get4byte(28+(u8*)pPage1->aData);
      testcase( nPage==0 );
      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
      testcase( pBt->nPage!=nPage );
      pBt->nPage = nPage;
      releasePage(pPage1);
    }
    assert( countWriteCursors(pBt)==0 );
    pBt->inTransaction = TRANS_READ;
  }

  btreeEndTransaction(p);
  sqlite3BtreeLeave(p);
  return rc;
}







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page1_init_failed:
  releasePage(pPage1);
  pBt->pPage1 = 0;
  return rc;
}

#ifndef NDEBUG
/*
** Return the number of cursors open on pBt. This is for use
** in assert() expressions, so it is only compiled if NDEBUG is not
** defined.
**
** Only write cursors are counted if wrOnly is true.  If wrOnly is
** false then all cursors are counted.
**
** For the purposes of this routine, a cursor is any cursor that
** is capable of reading or writing to the databse.  Cursors that
** have been tripped into the CURSOR_FAULT state are not counted.
*/
static int countValidCursors(BtShared *pBt, int wrOnly){
  BtCursor *pCur;
  int r = 0;
  for(pCur=pBt->pCursor; pCur; pCur=pCur->pNext){
    if( (wrOnly==0 || pCur->wrFlag) && pCur->eState!=CURSOR_FAULT ) r++; 
  }
  return r;
}
#endif

/*
** If there are no outstanding cursors and we are not in the middle
** of a transaction but there is a read lock on the database, then
** this routine unrefs the first page of the database file which 
** has the effect of releasing the read lock.
**
** If there is a transaction in progress, this routine is a no-op.
*/
static void unlockBtreeIfUnused(BtShared *pBt){
  assert( sqlite3_mutex_held(pBt->mutex) );
  assert( countValidCursors(pBt,0)==0 || pBt->inTransaction>TRANS_NONE );
  if( pBt->inTransaction==TRANS_NONE && pBt->pPage1!=0 ){
    assert( pBt->pPage1->aData );
    assert( sqlite3PagerRefcount(pBt->pPager)==1 );
    assert( pBt->pPage1->aData );
    releasePage(pBt->pPage1);
    pBt->pPage1 = 0;
  }
................................................................................
  if( rc==SQLITE_OK ){
    rc = sqlite3BtreeCommitPhaseTwo(p, 0);
  }
  sqlite3BtreeLeave(p);
  return rc;
}






















/*
** This routine sets the state to CURSOR_FAULT and the error
** code to errCode for every cursor on BtShared that pBtree
** references.
**
** Every cursor is tripped, including cursors that belong
** to other database connections that happen to be sharing
................................................................................
      int nPage = get4byte(28+(u8*)pPage1->aData);
      testcase( nPage==0 );
      if( nPage==0 ) sqlite3PagerPagecount(pBt->pPager, &nPage);
      testcase( pBt->nPage!=nPage );
      pBt->nPage = nPage;
      releasePage(pPage1);
    }
    assert( countValidCursors(pBt, 1)==0 );
    pBt->inTransaction = TRANS_READ;
  }

  btreeEndTransaction(p);
  sqlite3BtreeLeave(p);
  return rc;
}

Changes to test/misuse.test.

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do_test misuse-4.3 {
  set v [catch {
    db eval {SELECT * FROM t1} {} {
      set r [sqlite3_close $::DB]
    }
  } msg]
  lappend v $msg $r
} {0 {} SQLITE_BUSY}
do_test misuse-4.4 {
  # Flush the TCL statement cache here, otherwise the sqlite3_close() will
  # fail because there are still un-finalized() VDBEs.
  db cache flush
  sqlite3_close $::DB
  catchsql2 {SELECT * FROM t1}
} {1 {library routine called out of sequence}}







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do_test misuse-4.3 {
  set v [catch {
    db eval {SELECT * FROM t1} {} {
      set r [sqlite3_close $::DB]
    }
  } msg]
  lappend v $msg $r
} {1 {callback requested query abort} SQLITE_BUSY}
do_test misuse-4.4 {
  # Flush the TCL statement cache here, otherwise the sqlite3_close() will
  # fail because there are still un-finalized() VDBEs.
  db cache flush
  sqlite3_close $::DB
  catchsql2 {SELECT * FROM t1}
} {1 {library routine called out of sequence}}